Sol–gel prepared (Ga1−xInx)2O3 thin films for solar‐blind ultraviolet photodetectors

Abstract We prepared (Ga 1− x In x ) 2 O 3 thin films at 900 °C using a sol–gel method, from a 2‐methoxyethanol solution of gallium isopropoxide and indium isopropoxide stabilized by monoethanolamine on (0001) sapphire substrates. X‐ray diffraction showed that films prepared from solutions with an indium content below 0.4 are single phase with the same monoclinic structure as β‐Ga 2 O 3 and that increasing the indium content increases the lattice constants. Optical absorption showed that the band gap decreased linearly to 4.2 eV as indium content increased to 0.3. Planar geometry photoconductive detectors have been fabricated on the (Ga 1− x In x ) 2 O 3 thin films prepared from the solution with an indium content below 0.2. They showed photosensitivity in the solar‐blind region, and the long wavelength threshold of spectral response shifted toward longer wavelengths with an increasing indium content. Furthermore, heterojunction structures composed of Ga 2 O 3 and (Ga 1− x In x ) 2 O 3 were also fabricated and characterized by transmission electron microscopy and optical absorption.